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RSD: Diagnostic Sympathetic Block


- Discussion: 
   - response to sympathetic blockade is best diagnostic test for RSD; 
   - over 2/3 of patients will obtain significant relief; 
   - patient is given at least two successful stellate ganglion blocks; 
   - if patient has had a technically successful sympathetic block, and does not obtain significant relief, then the patient probably does not have RSD; 
   - successful stellate ganglion block is demonstrated by production of Horner's syndrome (constriction of pupil, ptosis of eyelid & warming of face), and warming of the extremity, diminished hidrosis; - motor and sensory function should be only minimally affected; 
   - because the sympathetic fibers are the least myelinated (as comparted to motor and sensory nerve fibers) these fibers are the first to be affected by the local anesthetic; 
   - if the patient achieves a complete motor and sensory block, then then the block cannot yield useful diagnostic information and should be repeated in the future; 
   - it is essential to question the patient about whether or not the stellate block produced warming and vasodilation of the extremity, because many patients will be "written off" as resistant to treatment when their diagnostic blocks were not successfully performed (technically inadequate); 

- Technique: 
   - stellate ganglion is located adjacent to C6-C7 vertebrae; 
   - typically the sternocleidomastoid and the underlying N/V bundle, are retracted laterally and the needle is inserted anterior to the muscle; 
   - failure to obtain relief after a successful blockade does not rule out dx of RSD, but relief after a stellate block virtually confirms dx